I am an old tech fart that has worked in the industry for 30 + years and need some help in solving a problem with my 03 3500 cummins. I lost the left turn signal and brake light feed to my trailer. line is dead from the front. wiring diagram shows relays for the right and left trailer lights. but no reference as to where they are. truck has factory 7 way plug. Any ideas?

 

I have the same problem.....someone please help. all the wiring and fuses are good.....clicking coming from power module....is it bad? left trlr. turn fine but no right turn or brake light to 7 way pin....HELP

 

I did confirm the problem is in the power module. You can have it repaired or buy a new or used one. there is also a quick fix of running a jumper wire from the truck's turn to the trailer plug but don't over load it.